Hi, Pyweed.
I would describe the Amazon sales as "mostly final". One of our challenges has been integrating our site into their somewhat different sales model. In general we will eat the cost of a small reversal / cancellation from Amazon, but will reverse the transaction for higher-dollar cards if Amazon notifies us within a few hours. Once we've actually started physically processing the order, we eat the cost if it's cancelled or if the payment doesn't go through.